The invention relates generally to wind turbine rotor control systems, and more particularly, to automatic pitch control systems for wind turbines. Prior to implementation of the rural electrification program, wind driven electrical generators were in common use primarily for direct current generation. Up until at least 1950, these wind turbines were all variable speed. Some of them employed blade load parameters for rotor controland blade feathering for RPM control. For example, the Jacobs hub, the Allied hub and the Win Power hub all utilized blade centrifugal loads to control peak RPM. Following the renewed interest in wind power in the past decade, various new rotor control systems have been developed. First, feathering controls have been developed to reduce blade pitch in response to RPM or rotor power. Second, stall controlling systems have been designed for increasing the blade pitch to stall the air foil thereby limiting rotor RPM or rotor power. Third, rotors have been designed with no pitch control but which by design stall out at specific power outputs and require a secondary system for protection in the case of loss of load or high winds. Fourth, rotors can be automatically turned out of the wind for speed control. Feathering control systems currently in use all require active RPM sensors to activate hydraulic systems, some with the assistance of microprocessors.
In order to be economically feasible for rural and residential use today, wind turbines operating in the three to six kilowatt regime must be extremely reliable, low cost, low maintenance systems with longevity on the order of twenty years. The system must accommodate gusts on the order of 125 miles an hour and continue operating in any weather conditions including ice buildup on the blades. Because of the extrememly harsh environment and longevity of the installation, simple mechanical systems are greatly preferred to electronic apparatus. In addition, some means for manual shutdown from the ground, particularly when servicing the unit, is most desirable. To protect the system from large amplitude vibrations caused by mechanical failures such as loss of a blade or excessive ice buildup, it would be extremely desirable for the system to shut itself down automatically.